Thiazolocarbocyanine dye and process of preparing it



Patented Mar. 1 9, 1935 UNITED STATE-S o 1 9 3 PATENT OFFICE V r "1,994,553 THIAZOLOCARBOCYANINEDYE AND a PROCESS OF PREPARING IT Leslie G. S. Brock er, Rcchester, N..Y., assignor to "Eastman'Kodak com any, Rochester, N. Y., a a corporation of New York N0 Drawing. Application June 29, 1932, Serial N0. 619,962

16 Claims. (01.526044 This invention relates to new compounds and particularly to a new class of photographic sensitizing dyes, termed thiazolocarbocyanines, and methods for the preparation thereof.

In my co-pending application No. 548,025," it was mentioned that certain dyes, for which the name "neothiazolocarbocyanine" -isproposed, could be prepared from bases-of the thiazole series. It was further stated in that application that these neothiazolocarbocyanines were produced when certain alkyl quaternary salts of the thiazoles were treatedwith ethyl orthoformate in pyridine solution.- The alkyl quaternary salts of the bases which are most suitable for the preparation or" the neotl'iiazolocarbocyanines are'those of alkylsulfuric acids or, better still, arylsulfonic acids. It was further mentioned in my above application that in general a proportion of normal thiazolocarbocyanine accompanied the neothiazolocarbocyanine, and in most instances the normal thiazolocarbocyanine was more soluble than the neothiazolocarbocyanine and the latter could therefore be readily obtained infia state of purity.

It was stated in addition that the normal thiazolocarbocyanines were obtained when alkyl iodides of the specified thiazole bases wereco'rrdensed in'the presence of alkyl orthoformate and pyridine. As herein described, alkyl ortho-esters of a mono-carboxylic acid having more than one carbon atom yield '7-substitute'd thiazolocarbocyanines. These are related to the neothiazolocarbocyanines in that both dyes have a uriivalent roup attached to the carbon atom in the '7-position. 1

It is, therefore, among theobjects of the pres- 'ent invention to provide a process for the preparation of the thiazolocarbocyanines. A further object is to providea process for the preparation of the 7-substituted thiazolocarbocyanines. "Other objects will appear upon a further perusal of this specification. r V

The thiazole bases with a reactive methyl group in the 2-position may be given the general forgroupings. The numbering is that in common usage for bases of this type, being that used, for

instance in Richters Lexikon der Kohlenstoff Verbindungen.

The base 2-methylthiazole,"or a substituted 2- V 'methylthiazole, e. g. 2-methyl-4 phenylthiazole, may beconverted into-an alkylquaternary saltby heating it with, for instance,a 'dialkylsulfate or X is a suitable acidic radical.

an 'alkyl p-toluene sulfonate or=an alkyl iodide.

When the alkyl halides are used, quaternary alkyl iodides are produced which ontreatment with ethylor'thoformate and pyridine under appropriate conditions yield thiazolocarbocyanines.

The general reaction of alkyl quaternary "salts of 2-methylthiazoles with alkyl ortho esters of themonocarboxylic acids maybe written as follows- In the above equation -A and Bhave the significance given to them above, R stands for alkyl and The acidic radical X may be changed at will :by using the various methods of double decomposition. If the reestersinwhichR and R aresimilar or dissimilar but, as may be seen from the equation, these alkyl groups are removed as molecules of alcohol 'an'd-do'not enter the dye molecule. D is a suitable univalent atom or group, such as hydrogen, alkyl or aryl. If D-be hydrogen then the ester employed isderived from orthoformic-acidand X is best chosen as iodide for the main product of the reaction to be normal 'thiazolocarbocyanine of the type: i a

A s s A g CH=CHOH= u g R X R as has already been explained, since choice of, -for example, -p-tdluenesulfonate for X results in -apreponderance of the special type of 7-substituted thiazolocarbocyanines known as neothiazolocarbocyanines. In most cases however, some normal thiazolocarbocyanine is produced even when X is p-toluenesulfonate or alkylsulfate, but if the normal compound is desired it is recommended that iodide be chosen for X and this results in the product in general being almost pure normal compound. n

If D represent a univalent group such as methyl or ethyl (CH3 or C2H5) then it is immaterial whether X represents halide, p-toluenesulfonate, alkylosulfate or the like, as far as the type of compound is concerned. In all cases the 7-substituted dye is produced. The yield of product, however, may vary with the acidic radical employed, and in general an aryl sulfonic radical is preferred for the condensations.

These new dyes are useful as sensitizers for photographic emulsions, such as gelatino-silverhalide emulsions, for the green portion of the spectrum.

The 2-methylselenazoles may be regarded as thiazoles in which the sulfur atom in the molecule has been replaced by a selenium atom. These new bases are described in my co-pending application with Frank L. White No. 619,959 filed of even date. Selenazolocarbocyanine dyes derived from the Z-methylselenazoles may be prepared in a manner similar to that herein described for the thiazolocarbocyanines.

In general it is desirable to employ an excess of the ortho ester over the amount (one molecular proportion of ester to'two molecular proportions of quaternary salt) shown in the equation. This results in an increase in yield. The ortho ester and the .quarternary salts are conveniently C011". densed together by refluxing them together in anhydrous pyridine, usually for an hour or longer. After the reaction is finishedthe dye may be precipitated as a tar by the addition of ether, the ethereal layer decanted and the tar dissolved in a little hot alcohol (methyl or ethyl) and precipitatedas, for instance, the iodide by an excess of aqueous potassium iodide, or in some cases the dye may be precipitated from the pyridine reaction mixture by the addition ofv water, and in still other cases the dye separates from the reaction mixture in the crystalline state. These methods are all simple procedures and-are well known in the. art.

EXAMPLE I 3,3',4,4-tetramethyZthiazolocarbocyanine iodide 4,4 dimethyZ-3,3' diethylthiazoZocarbocyanine iodide 2,4-dimethylthiazole ethiodide was made by refluxing the base with ethyl iodide for several days and washing the solid product with acetone to remove starting materials.

2.7 parts of this ethiodide were refluxed for 5 hours with 30 parts of pyridine and 3 parts of ethyl orthoformate. The dye was precipitated After allowby diluting the reaction mixture with an equal volume of water and allowing to cool. The product was recrystallized from methyl alcohol in which it gave a crimson solution and was ob-' tained in dark needles with a greenish reflex.

It has been'described in my co-pending application No. 548,025 Example V, that this dye may also be obtained together'withthe corresponding,

neothiazolocarbocyanine. Thefalmost pure normal thiazolocarbocyanine described in that example may begiven a further crystallization to render it completely pure.

EXAMPLE III 4,4 diphenyZ-3,3 T -dimethylthiazolocdrbocyanine iodide" r 4-phenyl2- methylthiazole methiodide; was

prepared by refluxing equal weights of 4 -phenyl- Z-methylthiazole and of methyl iodide for two days. The solid alkyl quaternary saltwas removed-ground finely underacetone, filtered off and washedwith acetone and dried.

2 parts of the methiodide obtained above were ExAivirtn IV 4,4 diphenyZ-3,3 diethylthiazolocarbocyanirie iodide 4-phenyl-2methylthiazole ethiodide was pre-: pared by heating 4-phenyl-2-methylthiazole with ethyl iodide under reflux for 50 hours. .The solid ethiodide was removed, pulverized and washed free from starting materials with acetone. 3.3 parts of the salt'were heated under reflux with 30 parts of anhydrous pyridine and ,3

parts of ethyl. orthoformate for 1 /2 hours. :The

reaction mixture was then diluted with an equal volume of water and allowed to'cool. crystals of the dye separated out which were purified by recrystallization from a small quantity of methyl alcohol.. The dye formed small greenish'crystals and gave a crimson solution-in 55 the solvent. r r EXAMPLE V The dye was obtained as small encountered 1 Bronze 4,4-dimethyZ-3,3',7-triethylthidzolocarbocydpine v iodide 225' parts of 2,4-dimethylthiazole wereconverted into the etho-p-toluenesulionate of the base by heating it with 4 parts of ethyl-p-toluenesulfonate at 130140 C. for six hours. crude quaternary salt (a viscous melt) was then refluxed without further purification with 20 parts of pyridine and 7 partsof ethyl orthopropionate for 2 hours. After allowing the' reaction'mixture' to cool, the dye was precipitated by the addition of ether, the ethereallayer decanted ofi and the tar dissolved in a little warm methyl alcohol and precipitated as the iodide by adding thereto a solution of 10 parts potassium iodide dissolved in parts: of water. After al- The lowing the whole to stand aside for several days the dye was removed byflltration and puriiiedby 50 parts of hot water.

4,4 diphenyl 3,3',7 trimethzllthiaolocarbocy anine zodide 3.5 parts of 4-phenyl-2-methyl thiazole were converted into the metho-p-toluenesulfonate of the base by heating with 3.7 parts of methyl-ptoluene'sulfonate at 100 C. overnight. The crude 4-phenylZ-methylthiazole metho-p-toluenesulfonate was then refluxed for 90 minutes with 10 parts of pyridine and 4.8 parts of methyl orthoacetate. The dye was then precipitated as the sparingly solubleiodide by double decomposition with a solution of 5 parts of potassium' io'dide in The dye separated as a tarry residue, and after the aqueous liquor had been removed, this residue was washed. The purplish black powder was purified by recrystallization from methyl alcohol and the dye was thus obtained as small greenish crystals with a bright lustre. The solution of the dye in methyl alcohol was a crimson color.

EXAMPLE VII 4,4 diphenyl 3,3 dimethyl- 7 -ethyZthz'aeoZo carbocyanine iodide 3.5 parts of 4-phenyl-2-methylthiazole were condensed with 3.7 parts of methyl-p-toluenesulfonate as described in Example VI. The quaternary salt was refluxed without further purification with 5.4 parts of methyl ortho-propionate and 10 parts of pyridine for 90 minutes. The dye was precipitated as the iodide exactly as described for the dye in Example VI and was purified and recrystallized in the same manner also. The dye gave a crimson solution in methyl a1cohol and crystallized in small green crystals with a green luster.

From the foregoing it becomes apparent that thiazolocarbocyanines may be prepared by condensing two molecular proportions of a Z-methylthiazole alkyl quaternary salt with one molecular proportion of an ortho ester of a monocarboxylic acid. The thiazole may have either hydrogen or a suitable univalent group in one or both of the 4, 5 positions. If an ortho ester of formic acid is employed, an unsubstituted .thiazolocarbocyamne will be obtained. If an ortho ester of a monocarboxylic acid other than formic acid is employed, a 7-substituted thiazolocarbocyanine is obtained. These ortho esters are described in my Patents Numbers, 1,846,301, 2, 3 and 4, and need not be repeated here.

Other variations and equivalents will doubtless occur to those skilled in this art, it being understood that the foregoing is stated only to illustrate to those skilled in the art how thiazole alkyl quaternary salts may be condensed with an ortho ester of a monocarboxylic acid to form a thiazolocarbocyanine.

What I claim as my invention and desire to secure by Letters Patent of the United States is 1. A process for the preparation of thiazolocarbocyanines which comprises condensing, under the influence of heat, two molecular proportions of a thiazole alkyl quaternary salt with one molecular proportion of an ortho-ester of an aliphatic monocarboxylic acid in the presence of an organic base which is a solvent for the reactants andwhich acts to bind acid eliminated from the quaternary salt as aresult of the condensation.

. 2. A process for the preparation of thiazolocar bocyanines which comprises condensing one mo lecular proportion-of an ortho-e'ster of anauphatic monocarboxylic acid, under the influence of heat, with two molecular proportions of an alkyl quaternary salt represented by'the following structure: 1

R represents alkyl and X represents an acid radical.

3. A process for the preparation of thiazolocarbocyanines which comprises condensing, under the influence of heat, two molecular proportions of a thiazole alkyl quaternary salt with one molecular proportion of an ortho-ester'of an aliphatic monocarboxylic acid in the presence of an organic basewhich is a solventfor the reactants and which acts to bind acid eliminated from the'quaternary salt as a result of the condensation...

4. A process for the preparation of thiazolocarbocyanines which comprises condensing,.under the influence of heat, two molecular proportions of a thiazole alkyl quaternary salt with one m6- lecular proportion of an alkyl ortho-formate in the presence of an organic base which is a solvent for the reactants and which acts to bind acid eliminated from the quaternary salt as a result of the condensation.

5. A process for the preparation of thiazolocarbocyanines which comprises condensing, under the influence of heat, two molecular proportions of a thiazole alkyl quaternary salt with one molecular proportion of an alkyl ortho-acetate in the presence of an organic-base which is a solvent for the reactants and which acts to bind acid eliminated from the quaternary salt as a result of the condensation.

6. A process for the preparation of thiazolocarbocyanines which comprises condensing, under the influence of heat, two molecular proportions of a thiazole alkyl quaternary salt with one molecular proportion of an ortho-ester of a monocarboxylic acid in the presence of pyridine.

7. A process for the preparation of thiazolocarbocyanines which comprises condensing, under the influence of heat, two molecular proportions of a thiazole alkyl quaternary salt with one molecular proportion of an alkyl orthoi-formate, in the presence of pyridine.

8. A process for the preparation of thiazolocarbocyanines which comprises condensing, under the influence of heat, two molecular proportions of a thiazole alkyl quaternary salt with one molecular proportion of an alkyl ortho-acetate in the presence of pyridine.

9. A carbocyanine dye of the followingstrucin which A and B represent hydrogen, an ali- ..,...f in which A and 13 represent hydrogen, an aliphatic group or an aromatic radical of the benzene series,

phatic group or an aromatic radical .of the benvzene series, R equals alkyl, X equals an acid radical and D equals an alkyl group or an aryl group of the benzene series. A

R X e R in which A and B represent-hydrogen, an aliphatic group or an aromatic radical of the benzene series, R equals alkyl, X equals an acid'radical and. D equals an alkylgroup. i

11. A carbocyanine dye of the following strucin which A and B represent hydrogen, an ali- 'ture phatic group or an aromatic radical iof the-hen zene series, R equals alkyl, x'equals an'acid radical and D equals a methyl group.

12. A carbocyanine dye of the following strucsure 7 in which A and B represent hydrogen an aliphatic groupror an aromatic radical of thebem zene series, R equals alkyl, X equals an-acid radical and D equalsan ethyl group.- I i 13. A 3,3'.-dialkyl-7-alkyl-thiazolocarbocyan inesalt. J' A .v 14. A 3,3 -dialkyl 7 methyl-thiazolocarbooy-e anine salt. e a 15. A 4,4-dialkyl-3,8'-dialky1-7ealkyl-thiazolocarbocyanine salt. v s I 16. A 4,4-diaryl3,3'-dialkyl-'I-alkyl-thiazolocarbocyanine salt the aryl groups being or the benzene series.

LESLIE G. s. BRO OKERS 

